Huge audience … Oprah Winfrey in Steven Spielberg's 1985 film version of The Color Purple. Photograph: Moviestore Collection/Rex Features

The first page took your breath away: a mortified 14-year-old girl has started writing letters to God because she can tell no one else that, although "he never had a kine word to say to me", "he" [her putative daddy] has raped her and warned that she "better … git used to it". Page two, letter two: her mama dead and she "big" with her second baby. He "kilt" the first. "Kill this one, too if he can." Letter three: the letter-writer has a little sister she will protect "with God help". Letter four: sister Nettie has a friend named Mr ___. Letter seven: Mr ___ wants to marry Nettie but he carries a picture of a beautiful, worldly woman named Shug Avery in his wallet. The letter-writer is mesmerised by Shug Avery.

We in turn are mesmerised by the letter-writer's pitiable but profoundly perceptive, truthful voice. "Negro dialect", now called "folk speech": we might not have been ready for it before – thought it ignorant or demeaning, some of us – but we're ready for it now. This voice is clear, simple but not simplistic, allowing us no escape. Letter eight: Mr ___ will marry the letter-writer instead of Nettie, not because he likes her, but because – stupid and ugly as she is – she'll be a good worker. And she finally reveals her name. She is Celie, embarking on a 40-year journey that will take her from bewilderment, through degradation, bestowed and reciprocated love, to self-love and personal agency.

The Color Purple, a simple yet intriguing title, was published in 1982. Alice Walker, the eighth child of southern sharecropping parents, was 38 and already the author of three poetry collections, one volume of essays, two previous novels, and an editor of Ms. Magazine, the women's movement's well-financed and glossy American mouthpiece. In other words, she was not unknown to those of us who cared about the African-American female literary voice. Nor was the novel's terrain an unacknowledged world: a candid exploration of sometimes toxic relationships between black men and black women, the struggle of black women for self-appreciation and personal power. We had read of this in Zora Neale Hurston and Carlene Hatcher Polite, in Gayl Jones and Toni Morrison, heard it sung in countless blues as well as the poetry of Sonia Sanchez and Ntozake Shange to name but a few. But Walker's track record and The Color Purple's singular clarity made the outside (white) literary establishment take notice. In 1983, Walker became the first African-American woman to win both the Pulitzer and National Book awards for fiction, amid all hell breaking loose.

What Walker has defined as "womanism" caused an uproar in many corners of the African-American establishment, full of indignance at what was judged her "negative imagery" of the black male, the black family. We had been this way before, with Ntozake Shange's For Colored Girls Who Have Considered Suicide When the Rainbow Is Enuf in 1976, with Michelle Wallace's Black Macho and the Myth of the Superwoman in 1979, and with Toni Morrison's The Bluest Eye and Song of Solomon: creatively gifted and politically engaged African-American women dismissing black activist Stokely Carmichael's diktat that the "only position for a woman in [the revolution was] prone", and resisting the communal adage against airing dirty linen in public.

Morrison, exploring black female truths, refused to engage with this nonsense, kept her counsel and kept right on stepping, while the younger, more vulnerable Shange and Wallace were deeply wounded by the abuse; but this time, with The Color Purple, white folks were taking closer notice than they had before, awarding prizes, giving mainstream showtime. Some in the black community maintained that the only reason Walker and the rest of these women were getting this recognition was the white man's glee in the black man being put down. Better that its women remain invisible if this is all they had to say. Where were their loyalties?

Smouldering coals reignited two years later with the release of Steven Spielberg's film. It was the director's first "serious" drama, and to my mind referenced almost every known Hollywood coon cliche, from the Harlem sitcom Amos 'n' Andy to sultry sexpot mulattos, while treating Whoopi Goldberg's Celie as ET's equally alien first cousin, and simply ignoring the book's many subtleties in regards to Africa, the will and road to power, and unapologetic woman-to-woman love. Yes, it was a film, but this was supposed to be The Color Purple, not some Hallmark greeting card.

However, out in hinterlands, black women, seeing themselves on screen with sympathy and dressed in dignity, came in their droves. The film's success laid the groundwork for the still soft but more mature stage version, which I saw on Broadway in 2005 – not least because Oprah Winfrey, who played Sofia in the film, is one of the musical's primary producers and her huge audience its primary target.

Rereading the book for the first time 30 years on, as the story appears on the London stage, I am struck by its elements of fable: though dangerous and demeaning white folk lurk just beyond its trees, its black community is sturdily prosperous and self-sufficient, its God manifest in colourfully abundant nature. I am struck, too, by its subtle discussion of the African-American relationship with our homeland, by the simple metaphor of Celie's folk pants, comfortable and flattering regardless of the shape and gender of the wearer; and by its ultimate generosity of spirit. For in the end, Mr ___ is redeemed in the manner Celie is redeemed, via self-discovery, self-acceptance and a willingness to let love just be – rather than try to control it, and the world.

•Candace Allen is the author of Soul Music: The Pulse of Race and Music.